The present invention relates to an operating unit provided with a device for automatically changing the tools, specifically designed for transfer tool machines.
The invention also relates to a transfer machine including the above mentioned operating unit.
As is known, transfer tool machines are conventionally used for carrying out machining operations on a metal workpiece supplied in a raw form, in order to transform the workpiece into a finished product, by transferring the workpiece from a starting inlet machining station to an end machining station, or outlet station, by a rotary table transfer assembly.
The mentioned machining operations are performed by operating units which, usually, are designed for receiving a single tool and which, accordingly, carry out a specific or set processing or machining operation.
Thus, it would not be possible to modify an operating unit designed at the start or set for performing milling operations, to transform it into a threading unit, provided that the machining tool is not manually replaced.
In order to provide a transfer tool machine with a greater operating flexibility, machining heads provided with a tool automatic changing system have been made (the so-called xe2x80x9cturretxe2x80x9d heads).
The latter substantially comprise rotary turrets, which are cantilever-wise mounted on a related machining unit and supporting a plurality of tool holder devices, each of which is in turn provided with a dedicated mandrel and respective bearings.
Owing to the rotary movement driving the turret head, a same operating unit can be used for performing different machining operations on a workpiece, without manually changing the related machining tool.
However, prior operating units provided with turret tool holder heads are affected by great drawbacks, mainly related to the comparatively great size and the cantilever-wise arrangement thereof on the operating unit.
In order to reduce the construction size, the prior art provides to design single tool holder devices of reduced dimensions, and, accordingly, small size mandrels and bearings therefor.
As a result, the strength of these devices is correspondingly reduced, with a less consequent capability of resisting against the mechanical stress to which said devices are subjected as the workpiece is machined (loads on the mandrel and bearings, vibrations, impacts and so on).
Thus, prior operating units, specifically designed for receiving great strength tool holders, and having consequently a large size, must be proportionately enlarged, to receive great strength mandrels and bearings.
The machining unit, accordingly, will have a comparatively great size, and, moreover, it can be provided with only a comparatively small number of tool holders, considering the maximum size which can be tolerated on such an apparatus.
Furthermore, the cantilever-wise arrangement of the above mentioned turret heads, would involve a great front size with respect to the transfer tool machine mandrel, which would cause space and handling problems, which are increased as the size of the tool holders is increased.
Accordingly, the aim of the present invention is to provide a novel operating unit, which has a very reduced constructional size with respect to prior machining unit, the mechanical strength of the tool holding devices being the same.
Within the scope of the above mentioned aim, an object of the present invention is to provide such an operating or machining unit which is specifically designed for making the size of the turret head independent from that of the tool holders.
Yet another object of the present invention is to provide such an operating or machining unit for transfer tool machines, in which the sizing of the tool holding devices does not affect the mechanical strength properties of said operating unit.
The above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by the operating unit and transfer tool machine as claimed in the independent claims 1 and 14.
Preferred embodiments of the invention are defined in the remaining claims.
With respect to a prior operating or machining unit, the operating unit according to the present invention provides the advantage of having a much smaller size, the mechanical strength of the tool holding devices being the same.
The operating unit according to the invention, moreover, provides the advantage that it it is much more simple and unexpensive construction wise, with respect to prior like operating units, owing to the use of a single mandrel, which is common to all of the tool holding devices.